Differential gene expression of bone-related proteins in epithelial and fibroblastic cells derived from human periodontal ligament.

Hertwig's epithelial root sheath (HERS) is involved in the differentiation of cementoblasts. The cells of epithelial rests of Malassez (ERM) may contribute to that process. However, little is known about the role of these epithelial cells in cementum repair. In the present study, we investigated the expression of alkaline phosphatase (ALPase), osteopontin (OPN), bone morphogenetic protein (BMP)-2 and BMP-4 in epithelial cells (E cells) and fibroblastic cells (F cells) derived from the same human periodontal ligament. E cells were identified by immunoblotting with anti-cytokeratin 5 and 8 antibody. Reverse transcription-polymerase chain reaction analysis showed that E cells have lower ALPase and BMP-4 mRNA levels than F cells. On the other hand, the expression of OPN mRNA in E cells was stronger than in F cells. No significant difference was observed in BMP-2 expression between E and F cells. Thus, they have different expression patterns of ALPase, BMP-4 and OPN, suggesting that ERM and mesenchymal cells in periodontal ligament may be cooperatively involved in cementum repair. Furthermore, E cell cultures will be useful in elucidating the role of ERM.